Critical to the fundamental development of a restraint system are the concepts of occupant energy management and occupant kinematics. In this regard, Federal Motor Vehicle regulations provide load limitations for various anatomical features of a seated occupant in a forward crash. These load limitations generally have been set to reduce the overall percentage chance of an injury for a given anatomical feature caused by a vehicle crash at a specific vehicle crash speed.
The individual components of a restraint system must be designed with the view of the other components in the restraint system, as well as the specific vehicle geometry. For example, the stiffness of an airbag cushion must be designed with view of the stiffness of a vehicle's steering column, windshield slope, and instrument panel stiffness. As such, it is very desirable during the development of a restraint system to have components which have easily modifiable engineering properties.
One integral component in any restraint system is the lower portion of the instrument panel or knee bolster. In this regard, the knee bolster functions to absorb a significant amount of an occupant's impact energy during a crash event. Further, the knee bolster is critical in a regulation of an occupant's kinematics. Specifically, the knee bolster regulates the angle an occupant rotates about its hip to encounter a deploying airbag. The regulation of the occupant's kinematics is a function of the load the knee bolster imparts onto an occupant's knees as well as the displacement of the knee bolster with respect to the vehicle. The travel of an occupant's hips within the vehicle is closely related to the translation of the knee bolster. It is known by those skilled in the art that the adjustment of the stiffness of the knee bolster can be used to reduce the likelihood an occupant will hit a windshield for an unbelted occupant during a crash event, by reducing the amount of rotation of an occupant's torso.
As such, it would be desirable to have a knee bolster for use in a restraint system which has engineering properties that can be easily tuned based upon vehicle geometry, occupant loading, and occupant displacement. It also would be desirable to provide a knee bolster which provides a steady state loading of an occupant's femurs so as to absorb as much energy during a crash event without exceeding government and industry set safety standards.
It is an object to the present invention to provide an instrument panel which overcomes the disadvantages of present knee bolster systems. Specifically, it is an object of the present invention to provide a highly tunable knee bolster which provides steady state loading of an occupant's lower extremities during a crash event.